In the manufacture of small electric motors, which are each fitted with a self-aligning bearing, it is difficult to reduce tolerances sufficiently to ensure that motors are not produced with too much clearance between the motor shaft and the bearing member of the self-aligning bearing. As a result, operation of these motors causes unacceptably high noise.
One way to overcome this difficulty is to resiliently bias the bearing member so that its axis is more steeply inclined to the axis of the bearing member housing than the motor shaft. This ensures that the bearing member is always inclined to the motor shaft so that the effective clearance between the motor shaft and the bearing member is effectively reduced and the noise produced on operation of the motor is also reduced.
In a known angularly blessed self-aligning bearing such as this, as disclosed in UK Patent Specification No. 2 226 090, a bearing member has an outer surface comprising first and second external surfaces formed around the axis of the bearing member; the first external surface is a part-spherical surface-of-revolution having a center of curvature lying on the axis of the bearing member; the second external surface is non-coincident with an imaginary spherical surface having the same center of curvature as the first external, part-spherical, surface-of-revolution and comprises at least one first portion which extends transversely of the axis of the bearing member; a housing for accommodating the bearing member has an internal surface-of-revolution, formed around the axis of the housing; first and second resilient retaining means are supported in engagement with the bearing member, with the second resilient retaining means engaging the second external surface; and the first and second resilient retaining means are resiliently distorted so as to urge the first external, part-spherical, surface-of-revolution axially into engagement with the internal surface-of-revolution, and to impose turning moments which tilt the bearing member by a predetermined amount relative to the housing.
In this construction, the second external surface comprises at least one first transversely extending portion which is the base of a notch formed in the first external, part-spherical, surface--of-revolution and the or each second resilient retaining means is a finger which differs in size and shape from the first resilient retaining means. Difficulty is therefore encountered in forming suitably accurate notches in the bearing member, which is usually of sintered construction, and in fitting the first and second resilient retaining means so that the fingers constituting the second resilient retaining means are correctly positioned in relation to the notches formed in the first external, part-spherical, surface-of-revolution.